(19) united statesdata.fs.usda.gov/research/patents/pub20140134415gong.pdf · 2014. 10. 21. ·...

US 20140134415A1

(19) United States (12) Patent Application Publication (10) Pub. No.: US 2014/0134415 A1

GONG et al. (43) Pub. Date: May 15, 2014

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SUSTAINABLE HYBRID ORGANIC AEROGELS AND METHODS AND USES THEREOF

Applicants:The United States of America as Represented by the Secretary of Agriculture, Washington, DC (US); Wisconsin Alumni Research

Foundation, Madison, WI (US)

Inventors: Shaoqin GONG, Middleton, WI (US); Alireza JAVADI, Madison, WI (US); Qifeng ZHENG, Madison, WI (US); Zhiyong CAI, Madison, WI (US); Ronald SABO, Sun Prairie, WI (US)

Assignees: The United States of America as Represented by the Secretary of Agriculture, Washington, DC (US); Wisconsin Alumni Research

Foundation, Madison, WI (US)

App1.No.: 14/077,103

Filed: Nov. 11, 2013

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Related US. Application Data

Provisional application No. 61/724,627, ?led on Nov. 9, 2012, provisional application No. 61/825,405, ?led on May 20, 2013.

Publication Classi?cation

Int. C1. C08] 9/00 (2006.01) C08] 9/28 (2006.01) US. Cl. CPC . C08] 9/0061 (2013.01); C08] 9/28 (2013.01) USPC .............. .. 428/219; 521/141; 521/64; 252/62

ABSTRACT

Highly porous, lightweight, and sustainable hybrid organic aerogels With ultra-low densities and excellent material prop erties and methods for preparing them are provided, includ ing, e.g., PVA/CNF/GONS, RF/CNF/GONS, and PVA/CNF/ MWCNT. The aerogels are modi?ed to have a super hydrophobic surface, thus leading to an extremely lOW swelling ratio and rate of moisture absorption.

Patent Application Publication May 15, 2014 Sheet 1 0f 17 US 2014/0134415 A1

FIG. 1

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US 2014/0134415 A1 May 15, 2014 Sheet 2 0f 17 Patent Application Publication

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Patent Application Publication M y 15, 2014 Sheet 5 0f 17 US 2014/0134415 A1


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May 15, 2014 Sheet 9 0f 17 US 2014/0134415 A1 Patent Application Publication

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US 2014/0134415 A1

SUSTAINABLE HYBRID ORGANIC AEROGELS AND METHODS AND USES

THEREOF

STATEMENT OF GOVERNMENT RIGHTS

[0001] This invention was made with government support under 11-JV-11111127-098 awarded by the USDA/FS. The government has certain rights in the invention.

TECHNICAL FIELD

[0002] The present technology relates generally to the ?eld of aerogel compositions and to various methods for produc ing the aerogel compositions. In addition, the present tech nology pertains to applications of the aerogel compositions and devices which utilize the new aerogels.

BACKGROUND

[0003] The following description is provided to assist the understanding of the reader. None of the information pro vided or references cited is admitted to be prior art to the present technology. [0004] Aerogels are lightweight materials that have drawn signi?cant attention due to their combination of unique prop erties including a high porosity (typically 95%-99%), low density (typically less than 400 kg/m3), high speci?c surface area, excellent thermal, acoustic, and electrical conductivi ties, and low dielectric constant. Over the past 70 years, researchers have mostly focused on developing inorganic aerogels such as silica, clay, and metal oxide aerogels. For instance, NASA has developed a series of silica-based inor ganic aerogels for various space applications such as launch vehicles, space shuttle upgrades, interplanetary propulsion, space suits, and life support equipment. Various types of inorganic-based aerogels have also been developed and com mercialized for applications in the structural insulation, clothing, aviation, automotive, and aerospace industries. However, inorganic (mainly silica) aerogels often suffer from intrinsic brittleness and a relatively high density (100-400 kg/m3), which consequently limits their use in applications where tough, strong, and low-density materials are required.

SUMMARY

[0005] The present technology provides hybrid organic aerogels having low densities and excellent mechanical prop erties suitable for a wide array of applications. The present hydrogels include a water-soluble organic polymer, cellulose nano?brils and/or nanocrystals, and carbon nanotubes or water-soluble graphene oxide. The water-soluble polymer and optionally cellulose nano?brils and/or nanocrystals may be cross-linked such that they are no longer water-soluble. These aerogels are highly porous with large surface to volume ratios and great speci?c compressive strength. [0006] The present technology further provides methods of making the hybrid organic aero gels and articles incorporating such aerogels such as various types of insulation and insula tors.

[0007] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features will become apparent by reference to the following drawings and the detailed description.

May 15, 2014

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a bar graph of the densities of illustrative embodiments of aerogels made from various formulations, including one or more of cellulose nano?brils, graphene oxide, and polyvinyl alcohol. The aerogels are either crosslinked (as indicated) or non-crosslinked. [0009] FIG. 2A is a graph comparing the compressive behaviors of illustrative embodiments of aero gels made from various formulations of cellulose nano?brils, water-soluble graphene oxide, and polyvinyl alcohol that are either crosslinked or non-crosslinked. For clarity, the legend lists the aerogel formulations in descending order to match the order at 80% strain on the x-axis (i.e. PVA/CNF/GONS (crosslinked), PVA/CNF (crosslinked), PVA/CNF/GONS, PVA/CNF, PVA (crosslinked), CNF/GONS, PVA, CNF, GONS). FIG. 2B is a graph comparing the compressive behaviors (at 80% strain) of illustrative embodiments of aero gels of different compositions as prepared in Example 4. [0010] FIG. 3 is a bar graph comparing the speci?c com pressive strengths of illustrative embodiments of aerogels made from various formulations of cellulose nano?brils, water-soluble graphene oxide, and polyvinyl alcohol that are either crosslinked or non-crosslinked. [0011] FIGS. 4A, 4B and 4C show SEM images of cellu lose nano?brils (4A), crosslinked polyvinyl alcohol (4B), and crosslinked polyvinyl alcohol/cellulose nano?brils/water soluble graphene oxide (4C) aerogels prepared via freeze drying. The scale bar is 2 pm. [0012] FIG. 5 shows contact angle measurements at differ ent times (in seconds) of a) pristine polyvinyl alcohol/cellu lose nano?brils/water-soluble graphene oxide aerogels, b) polyvinyl alcohol/cellulose nano?brils/water-soluble graphene oxide aerogels treated with Silane 1, and c) polyvi nyl alcohol/cellulose nano?brils/water-soluble graphene oxide aerogels treated with Silane 2, using water droplets. [0013] FIG. 6A is a graph showing the swelling character istics of illustrative embodiments of polyvinyl alcohol/cellu lose nano?brils/water-soluble graphene oxide aerogels before and after silane treatment. FIG. 6B is a magni?ed version of the bottom of FIG. 6A. For clarity, the legend lists the aerogel formulations in descending order to match the order at about 1400 minutes on the x-axis (i.e. PVA/CNF/ GONS (crosslinked) (off-scale), PVA/CNF/GONS (non crosslinked) silane 2, PVA/CNF/GONS (crosslinked) silane 2, PVA/CNF/GONS (non-crosslinked) silane 1, PVA/CNF/ GONS (non-crosslinked) silane 1). [0014] FIG. 7 is a graph of the weight loss of illustrative embodiments of polyvinyl alcohol/cellulose nano?brils/wa ter-soluble graphene oxide aerogels measured by thermo gravimetric analysis (TGA) as a function of temperature. For clarity, the legend lists the aero gel formulations in descending order to match the order at 700° C. on the x-axis (i.e. PVA/ CNF/GONS (crosslinked) silane 2, PVA/CNF/GONS (non crosslinked) silane 2, PVA/CNF/GONS (crosslinked), PVA/ CNF/GONS (non-crosslinked), PVA/CNF/GONS (non crosslinked) silane 1, PVA/CNF/GONS (crosslinked) silane 1). [0015] FIG. 8 is a bar graph comparing the BET speci?c surface areas of illustrative embodiments of polyvinyl alco hol/cellulose nano?brils/water-soluble graphene oxide aero gels, and their composites. [0016] FIG. 9 is an SEM image of (A) polyvinyl alcohol (25.42 kg m_3), (B) polyvinyl alcohol/cellulose nano?brils (26.83 kg m_3), and polyvinyl alcohol/cellulose nano?brils/

US 2014/0134415 A1

hydroxylated multiwalled carbon nanotube-1, 2, 3, and 4 aerogels witha density of(C) 14.55, (D) 20.13, (E) 26.00, and (F) 30.62 kg m_3, respectively, prepared by freeze-drying. The scale bars are 10 um and 2 pm for the main and inset pictures, respectively. [0017] FIG. 10A is a graph showing the compression stress-strain curves of polyvinyl alcohol, polyvinyl alcohol/ cellulose nano?brils, and illustrative embodiments of polyvi nyl alcohol/cellulose nano?brils/hydroxylated multiwalled carbon nanotube-3 aerogels at similar densities (~26 kg/m3). FIG. 10B is a graph showing the compression stress-strain curves of illustrative embodiments of polyvinyl alcohol/cel lulose nano?brils/hydroxylated multiwalled carbon nano tube-1, 2, 3, and 4 aerogels with varying densities. [0018] FIG. 11A is a graph showing the Young’s modulus (E*) of the exponential correlation of the yield stress (E*) and relative density (p*/ps) of illustrative embodiments of poly vinyl alcohol/cellulose nano?brils/hydroxylated multiwalled carbon nanotube aerogels. FIG. 11B is a graph illustrating the exponential correlation of the yield stress (0*) and relative density (p*/ps) of illustrative embodiments of polyvinyl alco hol/cellulose nano?brils/hydroxylated multiwalled carbon nanotube aerogels. [0019] FIG. 12A is a graph showing the thermogravimetric analysis (TGA) curves of illustrative embodiments of poly vinyl alcohol/cellulose nano?brils and polyvinyl alcohol/cel lulose nano?brils/hydroxylated multiwalled carbon nano tube-3 aerogels at a similar density (~26 kg m_3). FIG. 12B is a graph illustrating the TGA curves of illustrative embodi ments of polyvinyl alcohol/cellulose nano?brils/hydroxy lated multiwalled carbon nanotube-1, 2, 3, and 4 aerogels at different densities.

DETAILED DESCRIPTION

[0020] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components unless context dictates otherwise. The illustrative embodiments described in the detailed descrip tion, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. [0021] The technology is described herein using several de?nitions, as set forth throughout the speci?cation. [0022] For the purposes of this disclosure and unless oth erwise speci?ed, “a” or “an” means “one or more.”

[0023] As used herein, “about” will be understood by per sons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term. [0024] The embodiments, illustratively described herein, may suitably be practiced in the absence of any element or elements, limitation or limitations, not speci?cally disclosed herein. Thus, for example, the terms “comprising,” “includ ing,” “containing,” etc., shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described, or portions thereof, but it is recognized that various modi?cations are possible within the scope of the

May 15, 2014

claimed technology. Additionally, the phrase “consisting essentially of” will be understood to include those elements speci?cally recited and those additional elements that do not materially affect the basic and novel characteristics of the claimed technology. The phrase “consisting of” excludes any element not speci?cally speci?ed. [0025] As used herein, the term “and/or” shall also be inter preted to be inclusive in that the term shall mean both “and” and “or.” In situations where “and/or” or “or” are used as a

conjunction for a group of three or more items, the group should be interpreted to include one item alone, all of the items together, or any combination or number of the items.

[0026] One aspect of the present technology provides an aerogel which includes a water-soluble organic polymer, cel lulose nano?brils and/or nanocrystals, and water-soluble graphene oxide. In one embodiment, the water- soluble poly mer and optionally the cellulose nano?brils are cross-linked such that they are no longer water-soluble. [0027] Any suitable water-soluble organic polymer may be used in the present aerogel compositions. As used herein, the term “water-soluble organic polymer” means an organic polymer having a solubility in water of at least 1 mg/ml at 25° C. or an organic polymer comprising at least 90 mol % organic monomers that have a water solubility of at least 1 mg/ml at 250 C. In some embodiments the water-soluble organic polymer has a solubility of at least 5 mg/ml, at least 10 mg/ml, at least 25 mg/ml, at least 50 mg/ml, at least 75 mg/ml, at least 100 mg/ml or at least 150 mg/ml in water at 250 C. In some embodiments, the water-soluble organic polymer has a solubility greater than or equal to 100 mg/ml. In some embodiments, the water-soluble organic monomers of the water-soluble organic polymer have a solubility of at least 5 mg/ml, at least 10 mg/ml, at least 25 mg/ml, at least 50 mg/ml, at least 75 mg/ml, at least 100 mg/ml or at least 150 mg/ml in water at 250 C.

[0028] In some embodiments, the water-soluble organic polymer is a thermoplastic polymer. Suitable water-soluble polymers include, for example, polyvinyl alcohol, polyethyl ene glycol, polyacrylamide, polyacrylic acid, poly methacrylic acid, cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, chitosan, dextran, and dextran sul fate, or a combination of any two or more thereof. In some

embodiments, the water-soluble organic polymer is polyvinyl alcohol, polyethylene glycol, polyacrylamide, polyacrylic acid, polymethacrylic acid, or a combination of any two or more thereof. In some embodiments, the water-soluble poly mer is polyvinyl alcohol (PVA). [0029] In some embodiments, the water-soluble organic polymer is a thermoset polymer which comprises at least 90 mol % water-soluble organic monomers (e. g., having a water solubility of at least 1 mg/ml at 250 C. In some embodiments, the thermoset polymer comprises at least 90 mol %, at least 95 mol % or 100 mol % water-soluble monomers. However, it will be understood by those skilled in the art that the thermo set organic polymer of the present technology is an organic polymer cross-linked/cured at least to the extent that it cannot be signi?cantly softened or remelted by heat and is no longer water-soluble, despite including water-soluble organic monomers. Suitable thermoset polymers include, for example, polymerized resorcinol-formaldehyde, phenol formaldehyde, urea-formaldehyde, polyamic acid salt or a combination of any two or more thereof. In some embodi ments, the water-soluble monomers are resorcinol and form aldehyde which form resorcinol-formaldehyde thermosetting

(19) united statesdata.fs.usda.gov/research/patents/pub20140134415gong.pdf · 2014. 10. 21. ·...

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